1. Field of the Invention
The present invention relates to a device and method to accurately locate and position an encapsulated windshield in a vehicle.
2. Description of the Prior Art
Aerodynamic requirements for cars, trucks and other vehicles greatly influence their outside appearance. This aerodynamic influence is seen in the design of the windshield and the vehicle body, such as streamlining. The method of mounting windshield glass to a vehicle body affects the outside appearance and consequently, these aerodynamic requirements.
For trucks, the nature of the manufacturing process and tolerance stacking lead to a large number of cab build variations in the frame. For aesthetic reasons, it is necessary to hide these imperfections when installing the windshield.
One recent advance for windshield installation involves encapsulated windshields. Glass encapsulation molds a plastic trim piece, such as polyvinyl chloride, onto the periphery of the glass. The plastic trim piece fills the gap between the windshield glass and the vehicle body. The trim piece is injection molded after placing the windshield glass into the mold.
Although expensive, encapsulation provides a single unit for installation with excellent dimensional tolerances along the perimeter of the assembly. Encapsulation may also provide glass locating identification marks, mounting tabs, spacer blocks and exterior lip-type seals.
During vehicle assembly, the windshield is coated along its edges with an adhesive, frequently by a robot. The windshield is placed into the windshield opening of the vehicle frame and aligned. After insertion and alignment, the vehicle moves along the assembly line while the adhesive bonds the windshield to the vehicle, generally after several hours.
The encapsulated windshield must be accurately located and positioned both horizontally and vertically within the windshield opening, especially for an automated bond-in process. Tolerances for placement are very small. Therefore, accurately positioning the encapsulated windshield is critical because it affects both the fit and finish of the vehicle, as well as the quality of the bond. Without proper fit and bonding, air and water can leak into the vehicle.
Quickly mounting the windshield during production is equally important. The faster and more accurately the windshield is mounted, the less labor time is required. Therefore, the glass should be mounted without requiring lengthy adjustments. Trimming the vehicle or windshield and calculating the amount of adjustment to fit the windshield increase labor time, worker stress and the chance for error during production.
During assembly, the worker has a limited time to insert the windshield into the vehicle frame. Steps that require additional labor and calculations, especially sophisticated calculations, during production make it more difficult to economically and effectively install windshields. The additional time spent calculating variances and correcting for minor imperfections slows the assembly line. The greater number of calculations also increases the chance of introducing additional errors from miscalculation.
Furthermore, replacing windshields after assembly is difficult. Not only do the same problems exist with accurately positioning and installing the windshield, but the replacement windshields must incorporate the molded perimeter without changing the frame.
A prior method of installing a windshield uses three long, flat rectangular tabs (about 3 inches long) extending from a riveted metal bracket with an attached layer of plastic, such as sheet molding compound, forming the edge of the vehicle frame. One tab is located toward each side and the third is located in the middle. The windshield trim piece has a corresponding recess that matingly engages the tab.
Because the interlocking tabs and recesses prevent the worker from adjusting the fit by simply repositioning the window, correcting minor errors in fitting requires raising the windshield the full height of the tab or altering the tab or trim piece, such as by filing or shaving, to fit the windshield. The worker cannot simply shim the windshield, because there is no good location to place a shim. Raising the windshield to clear the tabs would increase the spring force generated from the trim piece compressed against the frame, leading to possible uneven bond or leaks in the cab. Because the tabs do not allow a gradual increase in trim coverage, the additional coverage at the top may be more than what is necessary, resulting in a poor finish.
The amount of tab or trim piece removed by this method is determined by trial and error and is time consuming. The alteration of the tab or trim piece must also be even and exact, or else the alteration itself will introduce error to the installation process. The worker must then calculate the amount of material filed away, adjust the position of the windshield to fit, modify the amount of adhesive and decide whether additional means are required to keep the windshield in place during bonding.
All of these additional steps to correct error are inefficient and costly. Cabs and windshields with slight imperfections may be rejected because they cannot be accurately installed. Because the cabs and windshields are expensive, this rejection is an expensive waste. Alternatively, correcting the slight imperfections may require these correction steps to be performed off the assembly line which also adds to the cost. Applying a plastic layer to the edge of the vehicle frame introduces an additional manufacturing step, further increasing the cost. Moreover, the tab design makes it extremely difficult to install a replacement windshield aftermarket.
Other methods use windshield markings to align the windshield. Although simple, the windshield is difficult to accurately position and maintain the position during assembly and bonding. Another method aligns windshield markings with a shallow notch within the frame. There is, however, no way of positively locking the windshield in position with these methods.
Therefore, one object of the invention is to design a frame and windshield that can be easily adjusted for minor errors. Another object is to properly and quickly position a windshield within a vehicle frame which requires minimum adjustments and calculations to correct for any error. Another object of the invention is to allow the method to serve as a quality control indicator for the frame itself. Still another object of the invention is to produce a frame where a replacement windshield easily installs.